1. Field of the Invention
The present invention relates to a recording apparatus which records on a sheet by discharging ink from a full-multiple ink jet recording head with a plurality of nozzles arranged in the direction crossing the direction in which the sheet is conveyed.
2. Description of the Related Art
Recording apparatus are divided into two types: one is of a serial type which alternately repeats the reciprocal movement of a carriage on which a recording head is mounted and the conveyance of a sheet; and another is of a line type which continuously records an image using a full-multiple recording head covering the width of a sheet.
Most ink jet recording apparatus perform a preliminary discharge by discharging ink, not for the purpose of recording, but to recover the apparatus from deterioration in the characteristics of ink in the nozzle of an ink jet recording head. U.S. Pat. No. 5,270,738 discusses a recording apparatus using a full-multiple recording head capable of performing the preliminary discharge.
U.S. Patent Application Publication No. US 2007/0291095 discusses a full-multiple recording head in which a substrate on which nozzles are formed is divided into a plurality of nozzle chips and staggered. The recording head has an area where the nozzles are overlapped in a nozzle array of adjacent nozzle chips in the direction crossing the conveyance direction. U.S. Patent Application Publication No. US 2007/0291095 discusses nothing about the preliminary discharge.
It is assumed that the full-multiple recording head including a plurality of staggered nozzle arrays preliminarily discharges ink onto the surface of the sheet.
When recording an image on the sheet, a number of discharges per nozzle in an overlapping part (overlapping area) is fewer than in a non-overlapping part (non-overlapping area). The preliminary discharge can be controlled such that the fewer the number of the discharges from the nozzle during the recording, the more the number of the preliminary discharges, in consideration of ink thickening. As a consequence, the number of the preliminary discharges from the nozzles in the overlapping area is greater than those in the non-overlapping area. As a result, a larger amount of ink is applied to the sheet in the overlapping area and the ink is transferred to the surface of a conveyance roller that contacts with the sheet, which may smear the conveyance roller. The ink stuck to the conveyance roller may be transferred to the sheet again after a single rotation of the conveyance roller.